Field of the Invention
The present invention relates to a canister for treating a fuel evaporated from a fuel supply source equipped for a vehicle such as an automobile.
Related Art
Generally, a canister of the kind mentioned above has a structure provided with a case member to which a fuel vapor introducing port, a purge port and an air (atmosphere) communication port and in which an adsorbent material (adsorption agent or adsorbent) is enclosed, a pad supporting the adsorbent material and a grid member pressing the adsorbent material and the pad in an axial direction thereof, and a filter element in form of sheet made of felt or like is disposed at an end portion of the grid member.
With the canister of the structure mentioned above, in a structure in which the fuel vapor introducing port is connected to a fuel tank and the purge port is connected to an internal combustion engine, if the internal combustion engine is stopped, the fuel vapor evaporated from the fuel tank is introduced into the canister through the fuel vapor introducing port to thereby adsorb and hold the fuel vapor by an adsorbent material so as to prevent the fuel vapor from being released externally into atmosphere. On the other hand, during a time when the internal combustion engine is operated, the fuel vapor adsorbed by the adsorbent material under a negative pressure is fed on the internal combustion engine side.
Further, during the operation of the internal combustion engine, although the air (atmospheric air) is introduced through the air communication port and the fuel vapor held by the adsorbent material is fed out on the internal combustion engine side, it becomes necessary to appropriately filtrate dust and/or dirt contained in the air. Because of such reason, there have been proposed some known structures for filtrating such air, and in one known example, a filter element made of felt or like material is disposed at an end portion of the location of the adsorbent material.
There has been also known a conventional structure in which an air passage is formed to a case member so that the air introduced through the air communication port, as disclosed in Patent Document 1 (Japanese Patent Laid-open No. 2003-3915).
A canister disclosed in the Patent Document 1 is configured such that an air passage is provided in the vicinity of an air communication port to remove dust and dirt contained in the air (atmospheric air), and hence, such arrangement contributes to prevent the filter element from being clogged.
However, in the canister disclosed in the Patent Document 1, the air passage is formed inside the case member, and hence, the structure of the canister is made complicated, and in addition, since the above structure includes members such as filter element and grid member which are arranged in the conventional structure, the number of members or parts increases. Thus, manufacturing cost also increases, being inconvenient and disadvantageous.